Memory is one type of integrated circuitry and is used in computer systems for storing data. Memory is typically fabricated in one or more arrays of individual memory cells. The memory cells might be volatile, semi-volatile, or non-volatile. Non-volatile memory cells can store data for extended periods of time, and in many instances including when the computer is turned off. Volatile memory dissipates and therefore requires being refreshed/rewritten, and in many instances multiple times per second. Regardless, the smallest unit in each array is termed as a memory cell and is configured to retain or store memory in an least two different selectable states. In a binary system, the storage conditions are considered as either a “0” or a “1”. Further, some individual memory cells can be configured to store more than two bits of information.
Integrated circuitry fabrication continues to strive to produce smaller and denser integrated circuits. Accordingly, the fewer components an individual circuit device has, the smaller the construction of the finished circuit can be. Likely the smallest and simplest memory cell is comprised of two conductive electrodes having a programmable material received there-between. Example materials include metal oxides which may or may not be homogenous, and may or may not contain other materials therewith. Regardless, the collective material received between the two electrodes is selected or designed to be configured in a selected one of at least two different resistive states to enable storing of information by an individual memory cell. When configured in one extreme of the resistive states, the material may have a high resistance to electrical current. In contrast in the other extreme, when configured in another resistive state, the material may have a low resistance to electrical current. Existing and yet-to-be developed memory cells might also be configured to have one or more additional possible stable resistive states in between a highest and a lowest resistance state. Regardless, the resistive state in which the programmable material is configured may be changed using electrical signals. For example, if the material is in a high-resistance state, the material may be configured to be in a low resistance state by applying a suitable voltage across the material.
The programmed resistive state is designed to be persistent in non-volatile memory. For example, once configured in a resistive state, the material stays in such resistive state even if neither a current nor a voltage is applied to the material. Further, the configuration of the material may be repeatedly changed from one resistance state to another for programming the memory cell into different of at least two resistive states. Upon such programming, the resistive state of the material can be determined by appropriate signals applied to one or both of the two electrodes between which the material is received.